Hydraulic fracturing is a process that creates fractures in rock formations (or reservoirs), which has the effect of increasing the output of a well. The most important industrial use of this process is for stimulating oil and gas wells.
Hydraulic fracturing helps remove natural gas and oil from rock formations deep within the earth's crust where there are insufficient porosity and permeability levels to allow these resources to flow from the reservoir to the wellbore at economic rates. Man-made fractures are normally extended into targeted rock formations and are typically created using wellbores drilled into the formations to enhance oil and natural gas recovery, such as from coal beds and shale rock, etc. In such case, the fractures preferably provide a conduit or path that connects the reservoir to the well, thereby increasing the area from which natural gas and oil can be recovered.
While “fracking,” as this technology has been termed, has increased oil and gas production, the environmental questions and concerns associated with fracking have continued. These concerns include contamination of ground water, risks to air quality, the migration of gasses and chemicals to the surface, the creation of seismic events, and the potential mishandling of waste. The potential costs associated with environmental clean-up, loss of land value, and human and animal health concerns are still being investigated and evaluated.
At the same time, it is clear that fracking has already significantly increased the output of oil and gas here in the United States. And with a significant number of new oil exploration efforts being made, especially on private land, over the last few years, the energy industry has not only seen the discovery of many new supplies being developed, but also a significant increase in the supply of oil and gas for commercial use.
Notwithstanding this success, the use of these technologies and the exuberant exploitation of these natural resources, has also led to some unintended consequences which haven't necessarily good for the energy industry. For one thing, it is believed that the over-supply of oil in this country resulting from increased fracking has led to a dramatic drop in oil prices throughout the world, i.e., the price of crude oil has dropped from over $100 per barrel to under $45 per barrel in less than six months, which has affected the global economy. Although some experts suggest that this has been caused in part by the slow-down in the overall global economy, which has led to less demand for oil throughout the world, many experts believe that had the supply of oil not been so dramatically increased by fracking here in the U.S., the price of crude oil would not have dropped so dramatically.
And because of this drop, many energy companies are now seeing their profits and margins slashed significantly, and in many cases, they are incurring huge losses and experiencing many shut-downs and lay-offs, and even facing bankruptcies, which is threatening to derail the new “energy renaissance” here in the U.S.
While existing oil wells and reservoirs are continuing to operate, and many of them are still thriving by producing significant amounts of oil, under these economic conditions, the potential for new explorations and new investments being made, along with new resources being found and exploited, have significantly been reduced. Without the increased margins and profits derived from higher oil and gas prices necessary to make these exploration and investment efforts worthwhile, many companies are now scaling back their operations and even terminating the many new projects and project development efforts they had in their pipeline.
At the same time, a number of oil wells have been abandoned over the last several years, which is due in part to a number of factors, including 1) the additional availability of new and more efficient resources including oil wells that have gone on-line, which have provided increased output at higher rates, making their efforts more profitable, 2) over time, as is the case with any existing oil reservoir, there is a tendency for the production levels and profitability rates to drop, as the accessible supply of oil gradually becomes depleted, and 3) the reduction in the ability of energy production companies to extract all of the remaining oil in an existing reservoir, due to the fact that over time the oil remaining near the bottom of the reservoir is thicker and more viscous and therefore more difficult to pump using conventional equipment. As a result of these issues, many energy companies are abandoning existing oil wells and reservoirs in favor of seeking newer and richer supplies and resources.
Under these circumstances, and with oil prices and therefore profits and margins being dramatically reduced, a need currently exists to find a cost-effective way to enhance the recovery of oil remaining in abandoned oil wells that exist across this country, as a means of augmenting the supply of oil coming from new oil reservoirs that are currently being exploited and developed. One advantage to recovering oil from an abandoned oil well, rather than exploiting new resources, is that with an existing reservoir no new land-use permits or environmental impact studies have to be performed and obtained. This enables the recovery of oil from these existing sites and resources to be less costly, and involve less upfront capital and fewer investments and risks, etc., as well as reduce the long term impact on the environment.
As further background, a typical oil well normally goes through several phases. In the beginning, when a new oil field is discovered and production wells are initially drilled into a geological formation, the phase it goes through is typically called the “primary production” phase, wherein oil is pumped and produced using the pent-up energy of fluids found in the reservoir. Then, at the end of primary production, in many cases, a considerable amount of oil can be left behind, with sometimes as much as 80 to 90 percent of the total amount of oil being “trapped” in the pore spaces of the reservoir. And depending on how productive a certain oil well has been in the past, and the cost of trying to extract the remaining oil versus the cost of exploiting a new site, energy companies have often chosen to abandon these reservoirs.
On the other hand, if an energy company desires to try to extract the remaining oil from the existing reservoir, and they do not abandon the site after primary production phase, they can move into what is called the “secondary production” phase, wherein a substance (usually water) is injected into the existing reservoir to pressurize the oil which allows the remaining oil in the reservoir to be more easily recovered. In such case, the injection of fluid helps to increase air pressure inside the reservoir, which helps to push and ultimately sweep the oil toward the recovery wells, i.e., either through new recovery pipes that are drilled into the formation for this purpose or through the original injection pipe that can be converted into a recovery pipe. This secondary production phase often yields up to an equal or greater amount of oil when compared to the amount recovered using primary production methods.
After both primary and secondary production efforts have been used, in many cases, as much as 50 to 70 percent of the total amount of oil existing in a reservoir can still be left behind. This is because much of the oil in the reservoir is either bypassed by the injected fluid (since oil does not mix well with the water) or the remaining oil (particularly near the bottom) is often too thick or viscous and therefore too difficult to recover using conventional pumping equipment.
One current practice that has seen some marginal success in the industry is the use of enhanced oil recovery methods, often called “Tertiary Production” methods, as a means of recovering oil from abandoned oil wells, which is typically used after both the first and secondary production phases have already been performed. These tertiary methods can include the injection of carbon dioxide gas into the existing oil wells, which causes the gas to react with the remaining oil, which in turn, helps to change the oil's properties, which then allows it to flow more freely toward the recovery pipes. In this respect, it has been found that when nearly pure carbon dioxide gas (that consists of greater than 95 percent of its overall composition) is mixed with oil, it has sufficient properties to cause the oil to swell, and become lighter, and in turn, less viscous, such that it will not only flow more easily through the reservoir, but also detach itself from the rock surfaces, which allows the oil to be pumped out using conventional equipment.
At the same time, it has been found that only about 4 to 15 percent of the remaining oil in a typical reservoir can be recovered using these tertiary methods, and therefore, this method has not always been viewed as being cost-effective to implement. Therefore, many existing oil wells are still being abandoned even though a significant amount of oil is left behind and remains in these existing reservoirs.
For all of the above reasons, a current need exists to develop cost-effective technologies for increasing the recovery of oil from abandoned oil wells, and in particular, in cases where the remaining oil in the reservoir is too viscous to pump out using conventional pumping equipment. There is also a need to develop improved technologies that will avoid harming the environment, such as the use of chemicals and the production of waste materials, etc.